Computer System Architecture MCQ - Central Processing Unit

6 Arrange the following configuration for CPU in decreasing order of operating speeds : Hard wired control, vertical micro-programming, horizontal micro-programming.

Hardwired control is the fastest. Since horizontal microprogramming involves lesser number of instructions, it is faster than vertical microprogramming.

7 The microinstructions stored in the control memory of a processor have a width of 26 bits. Each microinstruction is divided into three fields: a micro-operation field of 13 bits, a next address field (X), and a MUX select field (Y).
How many bits are there in the X and Y fields, and what is the size of the control memory in number of words ?

Control memory processor has 26 bit microinstruction divided into three field microoperation field is 13.
So, next address field (X) = 10
MAX select field = 3
Size of control = 2¹⁰ = 1024

Consider the following assembly language program for a hypothetical processor. A, B and C are 8 bit registers. The meanings of various instructions are shown as comments.
MOV B, # 0 ; B ⇽ 0
MOV C, # 8 ; C ⇽ 8
Z : CMP C, # 0 ; Compare C with 0
JZ X ; Jump to X if 0 flag is set
SUB C, # 1 ; C ⇽ C – 1
RRC A, # 1 ; Rotate right A through carry by one bit
JC Y ; Jump to Y if any carry flag is set
JMP Z ; Jump to Z
Y : ADD B, # 1 ; B ⇽ B + 1
JMP Z ; Jump to Z
X

8 If the initial value of register A is A₀ , the value of register B after the program execution will be